LONDON– Let’s imagine what post-Mobutu Congo could become. It has diamonds, copper and gold. It has rain and sunshine in abundance. It is not, given its immense size, overpopulated. It has wise political leadership, a stable democracy, economic and financial discipline and good governance. It is the heart of Africa, not Conrad’s “The Heart of Darkness.” In a word it is not the Congo it is Botswana which, bar the rain (Botswana is a desert country), could be the Congo’s twin. Botswana in the 1960s was one of the poorest African countries, far poorer than the Congo. Today it is a prosperous middle-income country. During the 1970s it grew at a world record breaking 16% a year and in the 1980s a handsome 11%. in the 1990s it suffered a few bumps when it was blighted by the worst drought of the century and the diamond market hit the floor. (Diamonds...